Paper about using existing radio sources for beacons

Just came across this interesting paper which proposes using existing
radio sources as beacons.

http://www.deviceforge.com/articles/AT8606455669.html

"by Anthony LaMarca (Sep. 9, 2005)

Foreword: This whitepaper introduces an open source toolkit that lets
mobile devices determine their locations with the aid of freely
accessible, nearby radio sources, such as fixed Bluetooth devices,
802.11 access points, and GSM cell towers. Basically, the device reads
the IDs of these local "radio beacons" (each of which has a unique or
semi-unique ID), looks up their positions in a locally-cached database,
and performs a computation akin to triangulation. Intel created Place
Lab in an effort to satisfy the emerging requirement for
location-awareness within mobile devices such as smartphones, PDAs, and
laptops, or even moving vehicles. According to the whitepaper, over
four million of the required radio beacons have already been mapped."

Joe Dunfee